I saw a bus, in front of the British Library, with an advert for the forthcoming Dorian Gray film plastered all over it. I'm not necessarily saying it will be bad, but the horror movie look of the poster, with Dorian Gray written in dramatic silver typeface, suggests this adaptation of Oscar Wilde's novel The Picture of Dorian Gray will have the same hyperbolic qualities as the film adaptation of Beowulf.

Anyway, it's piquant seeing this pumped-up ad for a 21st century Dorian Gray in front of the big orange gateway engraved with the British Library. It's kind of reassuring, actually. There's something about the subdued exterior of this research library that makes it hard to imagine, as you walk past, exactly how many manuscripts, early printed works and other unique literary treasures are housed within. The British Library, of course, holds the classics – but just what gives a work the gold-standard seal? Without getting too tangled up, let's look back at the bus on the street outside. Dorian Gray, the film it advertises, may be a monstrosity or a masterpiece. But the fact remains that a 19th century novel is being adapted into a 21st century film; even if it's terrible, the status of the original novel won't be harmed.

This is because elasticity is a key component of what makes a classic. You can do what you want to a classic – set Hamlet in outer space or have a monkey play the prince – and it will bounce back. It can be stretched and pummelled and it will always return to its original shape. The classics are classics because they are foolproof. Plagiarism enhances them. Satire strengthens them. The internet proliferates them. So here's to Dorian Gray – a classic.